Optical Absorption Line Shapes Due to Transition from Orbital Singlet to Triplet States of Defect Centers with Cubic Symmetry

Abstract

Structures in the optical absorption line shapes have been investigated for the transitions from orbital singlet to triplet states of defect centers with cubic environment. In the triplet excited states both the spin-orbit and the linear electron-lattice interactions have been taken into account. Under the classical Franck-Condon approximation, line shapes are specified by the combination of the four coupling constants which represent the strengths of the spin-orbit interaction and the Jahn-Teller interaction with one-, two- and three- dimensional lattice vibrational modes. For all the possible combinations of the four coupling constants, optical absorption line shapes have been numerically calculated by means of Monte Carlo integration method with sufficient accuracy. The results can be applied not only to the dipole-allowed transitions (F-bands, U ₂ -bands and C-bands in Tl ⁺ -like centers etc.) but also to the dipole-forbidden and vibration-allowed transitions in O _h and T _h environment. As an example of the application, Moran's results for the shapes of the F-bands in cesium halides have been criticized in the light of the present calculation.